Does the presence of desert dust modify the effect of PM10 on mortality in Athens, Greece?

Recent reports investigate whether windblown desert dust may exacerbate the short-term health effects associated with particulate pollution in urban centers. We have tested this hypothesis by using daily air pollution and mortality data for Athens, Greece during the period 2001-2006. We investigated the effects of exposure to particulate matter with aerodynamic diameter <0μg/m(3) (PM(10)) on total and cause specific mortality, during days with and without windblown desert dust, for all ages, stratified by age groups and by sex. We identified 141 dust days between 2001 and 2006. We used Poisson regression models with penalized splines to control for possible confounding by season, meteorology, day of the week and holiday effect. A 10μg/m(3) increase in PM(10) was associated with a 0.71% (95% confidence interval (CI): 0.42% to 0.99%) increase in all deaths. The effects for total and cause specific mortality were greater for those ≥ 75years of age, while for total mortality higher effects were observed among females. The main effect of desert dust days and its interaction with PM(10) concentrations were significant in all cases except for respiratory mortality and cardiovascular mortality among those < 75years. The negative interaction pointed towards lower particle effects on mortality during dust events. We found evidence of modification of the adverse health effects of PM(10) on mortality in Athens, Greece with desert dust events: the particle effects were significantly higher during non-desert dust days. Our analyses indicate that traffic related particles, which prevail on non-desert dust days, have more toxic effects than the ones originating from long-range transport, such as Sahara dust.